1. Field of the Invention
The invention relates to a method for testing a hearing aid, and to a hearing aid which has at least one microphone, one signal processing unit and one sound transducer.
2. Description of the Prior Art
It is known for hearing aids to be placed in a test box or a test room for technical testing. The test box or test room have good sound attenuation, which means that their interior offers effective protection against interference noise from the exterior. In order to avoid corrupting the test results, the acoustic conditions in the interior of the test box or the test room also must be virtually ideal. The walls of the test box or the test room thus are designed such that virtually no acoustic reflections occur at their surface. At least one speaker is located in the text box or the test room in order to direct sound at a hearing aid to be tested. In order to measure the actual level of a test signal which is introduced via the speaker, there is also at least one reference microphone within the test box or the test room. For testing, sound is directed at the hearing aid in the test box or in the test room, and the signal received by the microphone is read out and evaluated at a specific point in the signal path within the hearing aid, which starts from the microphone and runs via the signal processing unit to the sound transducer.
The test signals are stored on a data storage medium, for example a CD, or are generated by a computer including various parameters, for example in order to define the dynamic response or frequency range.
Such known test facilities have the disadvantage that they are complex, expensive and complicated to handle. They are therefore normally used only by hearing aid manufacturers or test laboratories.
An object of the present invention is to provide a method which simplifies testing of a hearing aid, and a hearing aid which can be tested more easily.
The invention is universally applicable to hearing aids. The hearing aid may in this case be a hearing aid that is worn behind the ear, a hearing aid that is worn in the ear or a pocket hearing aid. The signal processing may be carried out in analog or digital form. Furthermore, the hearing aid may have a single microphone or a multiple microphone system.
In the method according to the invention, a sound channel with a defined transmission response is first produced between the sound transducer and at least one microphone in the hearing aid. In the case of a behind the ear hearing aid, for example, this may be done by fitting a sound loop which leads from the sound transducer to the microphone. Open transmission of the sound originating from the sound transducer through the air surrounding the hearing aid to the microphone is pointless for testing, since this would result in too many incalculable interference influences. The transmission response of a closed sound channel between the sound transducer and the microphone is, in contrast, known, and can be taken into account in the evaluation.
An alternative option to fitting an external sound loop is to provide a corresponding sound channel for connecting the sound transducer to the microphone within the housing or on the housing at the manufacturing stage. In order to avoid feedback, this sound channel is preferably closed during normal operation of the hearing aid, and is opened only during testing. In this case, the hearing aid may have flaps or valves which can be operated manually or automatically in order to open or close the sound channel.
In a further method step, the normal signal path within the hearing aid, which runs from the microphone via the signal processing unit to the sound transducer, is interrupted. A test signal is then fed into the interrupted signal path. The test signal is then emitted either directly, or possibly after further processing, for example filtering or amplification, via the sound transducer of the hearing aid. It is passed via the sound channel to the microphone of the hearing aid, by which it is received for further processing and evaluation.
The method for testing a hearing aid according to the invention thus does not require either a test room or a test box. It can be carried out with simple means and without any complex test facilities. A largely automatic procedure can also be used for the test method, so that even the person using the hearing aid can test it without any specific specialist knowledge. In this case, it is possible to test virtually all the functions and characteristics of the hearing aid which can also be tested using a test box or test room. This includes, for example, the frequency response, or the response to different stimuli. There is no need for any reference microphone, as is normally used in a test box or a test room.
In order to take account of the change to the transmission response when the hearing aid is being worn, a variant of the method allows a coupler to be introduced into the sound channel between the sound transducer and the microphone. This coupler has an enclosed air volume of approximately 2 cm3, for example in order to simulate an average hearing response.
The method for testing a hearing aid becomes particularly simple and cost-effective if the test signal is stored in the hearing aid, or is generated in the hearing aid. If, furthermore, the signal received by the microphone likewise can be evaluated in the hearing aid, then a simple test of the hearing aid can be carried out without the assistance of any external test facilities. A hearing aid test thus can be carried out virtually at any time and anywhere.
To provide a conclusion as to the result of the test, the hearing aid emits a monitoring signal. The monitoring signal may be produced in audible form, for example by emitting specific tones or tone combinations which allow a conclusion about the result of the test, or by optical indication means on the hearing aid, for example in the form of an LCD or LED indication.
In order to obtain a detailed conclusion about the functionality of the hearing aid, it is connected, according to a further variant of the method, to an external test set for testing. The test set may be a standard computer in which specific test software is run in order to test the hearing aid. Test signals which are generated in the test set or are stored in it are transmitted from the test set to the hearing aid. The signals which are then, according to the invention, received by the microphone of the hearing aid, are subsequently transmitted back from the hearing aid to the test set. This variant allows considerably more comprehensive test and evaluation functions to be carried out than those which are feasible with the xe2x80x9cself-testxe2x80x9d described above, without any external test equipment. Due to the widespread use of computers and their simple and standardized handling, this method variant nevertheless offers advantages over known test methods, in which further, specific and expensive test facilities (test box, etc.) are required.
In order to test the hearing aid, it can be connected via a cable to a test set which, for example makes contact with the programming socket of the hearing aid and with a corresponding interface on the test set. There is thus no need for any additional interface on the hearing aid. Wireless communication between the hearing aid and the test set is also possible. For this purpose, both the hearing aid and the test set are provided with appropriate transmitting and receiving units.
Depending on the components of the hearing aid which are to be tested, the test signal can be fed in at different points in the signal path in the hearing aid. For example, in order to check the sound transducer and the microphone, the test signal can be fed directly into the signal path upstream of the sound transducer, and can be tapped and evaluated directly downstream from the microphone. All the signal processing circuitry thus is excluded from this test. The test signal may, however, entirely or partially pass through the signal processing unit, before being emitted via the sound transducer or before being tapped off in the signal path in the hearing aid. All the signal processing circuitry, or at least components of the signal processing circuitry, is then included in the test as well. This has the advantage of allowing a large number of adjustment options offered by modern signal processing units to be included in the test. In addition, faults within the signal processing unit can be traced and thus localized exactly by expedient choice of the points at which the test signal is fed into the signal path in the hearing aid and at which the signal received by the microphone is tapped.